201 unit 9
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what are the 3 overlapping functions of the nervous system?
- motor output
what is the sensory funtion of the nervous system?
senory receptors monitor and changes inside and outside of the body
what is integration?
processes and interprets sensory input;makes the decisions
what is motor output?
it dictates a response by activating effector organs
what is the CNS and what does it contain?
- it is the integrating and command center
- consists of the brain and spinal cord
what does the PNS consist of?
it consists of the nerves and Ganglia
what happens in the sensory (affrent) division?
signals get picked up by sensory receptors are carried by nerve fibers from the PNS to the CNS
what is somatic sensory?
- sense of structures external to the ventral bodyor of the outer tube.
- eg: skin, skeletal musculature, bones
what are general somatic senses?
- widely spread receptors
- eg: touch,pain,pressure,temp.
what are proprioceptive senses?
- they detect stretch in tendons and muscles
- body sense= position and movement of body in space
what are special somatic senses?
what are visceral sensory?
- sense of the viscer within the ventral body cavity or structures of the inner tube
- eg: digestive tube,lungs, heart, bladder
what are the general visceral senses?
- felt in the gi tract and urinary tract and reproductive organs
what is the special visceral sense?
what happens in the motor (efferent) division?
signals are carried away from the CNS to the PNS; innervate muscles and glands
what does somatic motor do?
- signals the contraction of skeletal muscles
- it is under voluntary control
- it is called the voluntary nervous system
what does visceral motor do?
- regulates the contraction of smooth muscle ,cardiac muscle,and glands
- controls the function of visceral organs
what are 2 other names for the visceral motor?
- the autonomic nervous system
- or the involuntary nevous system
what are the 2 major cell types?
what are neuroglial cells?
- they are suppport cells
- connective cells not nervous
- non excitable
- surround and wrap neurons
what are neurons?
- nervous cell
- transmits electrical impulses
what are the 6 types of neuroglial cells?
- microglial cells
- ependymal cells
- satellite cells
- schwann cells
what are astrocytes?
- most abundant cell in CNS
- take up and release ions to control the environment around neurons
- recapture and recycle neurotransmitters
- invovled with synapse formation in developing neural tissue
- produce molecules necessary for neural growth
- form the blood brain barrier
what are microglial cells?
- smallest and least abundant in CNS
- act as phagocytes;the macrophages of the CNS
- engulf invading microorganisms and dead neurons
- derived from blood cells called monocytes
what are ependymal cells?
- found in the CNS
- line the central cavity of the spinal cord and brain
- bear cilia which circulate spinal fluid
what are oligodendrocytes?
- wrap their cell processes around axons in CNS
- which produces myelin sheaths for the CNS
what are satellite cells?
they surround neuron cell bodies within ganglia in the PNS
what are schwaan cells?
- they surround axons in the PNS
- they preform an insulating layer
- prevent a leakage of currant
- increase the speed of impulse conduction(actionpotential)
what are mylein sheaths?
segmented structures composed of the lipoprotein myelin
what is the neurilemma?
thin layer of material external to myelin layers
what are the nodes of ranvier?
gaps along the axon where there are no myelin
overview of neurons?
- basic structure of the nervous system
- they conduct electrical impulses called action potential along the plasma membrane
- they live for a lifetime
- they do not divide
- they have a high metabolic rate
what are nissl bodies?
clusters of rough ER
what are nuclei?
clusters of neuron cell bodies located in the CNS
what are ganglia?
clusters of neuron cell bodies located in the PNS
what are dendrites?
short neuron processes (fibers) that transmit electrical singals toward the nerve cell body
what is the axon?
- the long neuron process (fiber)
- impulse generator and conductor
- each neuron has only one
- transmits impluses away from the cell body
where does action potential begin?
at the axon hillcock
where do axons end?
at knobs called axon terminals or synaptic knobs
what are tracts?
bundles of axons located in the CNS
what are nerves?
bundles of axons located in the PNS
what are multipolar neurons?
- more than 2 processes attatched to the cell body (usually many dendrites and one axon)
- the most common type
what are bipolar neurons?
- two processes attached to the cell body
- they are rare only found in some special sense organs like retina of the eye
what are unipolar neurons?
only a single process axon attatched to the cell body
how are the structures of neurons classified?
based on the numer of processes attatched to the cell body
how are the funtions of neurons classified?
based on the direction the nerve impulse travels
what are sensory (afferent) neurons?
- transmit impulses from the PNS to CNS
- all are unipolar
- neuron cell bodies found in ganglia within in PNS
what are motor (efferent) neurons?
- trnsmits from the CNS to PNS
- most are multipolar
- neuron cell bidies found in CNS
what are interneurons (association neuron)?
- confined to the CNS
- most are multipolar
- found between motor and sensory neurons
- neuron cell bodies located in CNS
where are mechanically gated ion channels found?
what do they open in response to?
- found in sensory neurons
- open in reponse to physical force like stretch pressure
what do chemically gated ion channels respond to?
respond to a variety of chemicals like neurotranmitters or intralcellular signal molecules
why are voltage gated ion channels important?
important in the initiation and conduction of electrical signals action potential
ions move ____ their concentration gradients, from _____solute concentration to _____ solute concentration.
in the Na+ K+ pump how many NA+ and K+ are pumped in or out/
3 Na+ are pumped out for every 2 K+ brought in the cell
electrical disequillibrium in the boddy is known as?
membrane potential or resting membrane potential
what is the equilibrium potential for K+?
what is the equilibrium potential for Na+?
what is the average resting potential for the cell?
what does the sodium potassium pump do?
it maintains the resting membrane potential.
what is the absolute refractory period?
the period of time where a second action potential can not be triggered no matter how large the stimulus
what is the relative refractory period?
- it follows the absolute refractory period
- the time when the depolarization potential is higher than normal it can iniate another action potential.
what 2 things increase conduction velocity?
- the diameter the thicker the axon the faster the action potential
- how well the axon is insulated with mylein, the more mylein the faster the action potential
what is saltatory conduction?
conduction along a myleinated axon
what is multiple sclerosis?
- symptoms include vision loss increased muscle weakness
- destroys mylein sheath of the CNS axons
- it stops action potential because there is to much distance between the nodes of ranvier
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